Gripping structure



Filed Feb. 23, 1966 4 Sheets-Sheet 1 in. M26 35 H V6 INVENTORS THOMAS N. EAGL ESON FIG. 2 GEORGE A. WINDISH BYMW ATTORNEY Dec. 17, 1968 1-. N. EAGLESON ETAL 3,416,350

GRIPPING STRUCTURE Filed Feb. 23, 1966 4 Sheets-Sheet 2 34b 32b 32 0 3O FIG. 3

46 (473/b 48 34a; 34b 70 32 ges 3/0 :W 320 f h r 77 78 42 1 I 58 F IG 4 INVENTORS THOMAS N. EAGLESON GEORGE A. WINDISH ATTORNEY Dec. 17,

EAGLESON ET AL 3,416,350

GRIPPING STRUCTURE 4 Sheets-Sheet 5 Filed Feb. 23, 1966 FIG. 6

INVENTORS THOMAS N. EAGLESON GEORGE A. WINDISH ATTORNEY United States Patent 3,416,350 GRIPPIN G STRUCTURE Thomas N. Eagleson and George A. Windish, Baltimore, Md., assignors to Martin-Marietta Corporation, New York, N.Y., a corporation of Maryland Filed Feb. 23, 1966, Ser. No. 529,512 Claims. ('Cl. 72-293) ABSTRACT OF THE DISCLOSURE A set of stretch press shock jaws comprises two opposed pairs of jaws having gripping surfaces defining an H-shaped cleavage. The four jaws are split, and by appropriate shimming, one set of jaws can accommodate a diversity of cross-sectional configurations of material to be gripped.

This invention relates to gripping devices and more particularly to a jaw for stretch-forming and like machines which is adapted to grip work pieces having various cross-sectional shapes with equal facility.

Stretch-forming machines use two opposed chucks or jaw arrangements between which is extended an elongate work piece to be formed to a selected shape. A desired bend or shape is imposed upon the work piece by moving one or both chucks relative to a die over which the work piece is bent, the chucks being so moved that the member is also stretched during bending.

The relatively high tensile forces required for such forming operations require the employment of chucks which are adapted to grip the opposing ends of each work piece in a manner imparting relatively uniform stresses over the work piece cross section. If the stress is not uniformly imposed, i.e., if the gripping force is only locally applied, stress concentration will cause the gripped material to rupture at or within the confines of the chuck during the forming operation.

To prevent such rupture, the prevailing practice is to provide the opposed chucks with jaw inserts which are custom designed and fabricated to accommodate the cross section of each of the various work pieces. Such custom fabrication involves the matching of jaw inserts to both the inner and outer surfaces of both web and flanges of the work piece. These jaw inserts are precision machined of hard, heat-treated tool steels and their fabrication is expensive and time consuming. Over a period of typically active stretch press utilization, a substantial inventory of jaw inserts will be collected as a result of the great number of work piece shapes now utilized in industrial activities. This collection amounts to a considerable investment on the part of the user.

Various designs have been proposed for a universal chuck arrangement accommodating a variety of work piece shapes. However, the proposals have not resulted in chucks imparting uniform gripping qualities matching those of the conventional custom-fabricated jaw insert arrangement.

The present invention will be seen to provide a gripping structure for a chuck retaining the desired qualities of customized jaw inserts while at the same time having a universal characteristic whereby it will accommodate many different work piece cross-sectional configurations.

The invention also has an object of providing a novel jaw insert arrangement which may be utilized without modification in conventional stretch-press chuck assemblies.

Another object of this invention is to provide a jaw arrangement which will apply a powerful and uniform gripping force.

A further object of this invention is to provide a fastacting jaw which will allow facile insertion and removal of the work piece to be gripped.

An additional object of the invention is to provide a stretch-press jaw insert arrangement which is convenient to use, easily installed in a working position and readily disconnected from a chuck assembly.

Another object of the invention is to provide a novel jaw insert arrangement which may be readily adapted to grip a variety of work piece configurations with the use of shim means.

The invention is further typified by its simplicity, economy of use and relative ease of manufacture.

The invention also encompasses novel details of construction and novel combinations of parts which, along with further and other objects, are described and illustrated by the following discussion and related drawings in which:

FIGURE 1 is a front view of a stretch press jaw illustrating a chuck housing and the jaw insert gripping structure of the invention.

FIGURE 2 is a sectional side-elevational view illustrating in partially cut-away fashion a stretch press jaw assembly taken along the line 2-2 of FIGURE 1.

FIGURE 3 is a plan view of the gripping structure of the invention.

FIGURE 4 is a sectional side view of the gripping structure illustrating certain of its interrelated components taken along the line 4-4 of FIGURE 3.

FIGURE 5 is an elevation view of the gripping structure taken along the plane of line 5-5 of FIGURE 3.

FIGURE 6 is a sectional view of the gripping structure showing certain of its components in cut-away fashion and taken along the line 6-6 of FIGURE 3.

FIGURES 7-12 are front views of a stretch press jaw showing a chuck housing and the jaw insert gripping structure of the invention shimmed to accommodate a variety of different work pieces.

Referring to FIGURES 1 and 2, a stretch press jaw assembly is illustrated comprising a chuck housing 10 mounted by housing extension 10a to one arm of a conventional stretch press. Disposed rearwardly within the assembly is a hydraulically or pneumatically actuated piston arrangement shown generally at 11 and comprising a cylinder 12 provided with a cylinder bore 13 in which is fitted a piston 14 having an extension 15 extending through a central bore in plate 16. Plate 16 has an annular recess 17 of dimension suificient to seat a head 18 during reciprocal movement of the piston assembly. A bore 19 forms a passage for fluid or air through plate 16 into the forward side of cylinder bore 13. Similarly, a passage 20 supplies driving fluid into cylinder bore 13 rearwardly of the piston. A customized bolt 21 along with Washer 22 and spanning slot 23 provide interattachment of the piston and extension assembly. A shallow recess 24 serves to receive the protruding bolt 21 during the rearward travel of the piston.

As will be evident to those familiar with the art, projection or retraction of piston 14 is accomplished by the selective control of fluid flow through the respective passages 19 and 20.

Housing 10 has an internal surface 26 of generally rectangular cross section, selected individual surfaces such as 27 of which are tapered to present a progressively restricting interior surface to a jaw assembly as it is urged outward toward the smaller forward face 28 of the h0using by the piston arrangement.

The foregoing description of a chuck housing and piston assembly is of a generally conventional assembly used in stretch press or the like machines. It is for use with the abovedescribed and similar chuck arrangements that the gripping structure of the instant invention is intended.

According to the present invention, the gripping structure shown generally at comprises a set of jaw inserts shown at 31a, b to 34a, b disposed upon a base plate 35. The structure 30 is attached at the base plate 35 to head 18 by such suitable means as machine bolts or the like (not shown). As will be evidenced from the drawing, projection of the piston extension 15 will force the jaw inserts into intimate contact with the internal housing surface, forcing the mutual contraction of the former to establish a compressive gripping force over the inserted portion of a work piece such as that shown at 100. To facilitate the description of the structure and operating characteristics of the gripping structure, the term transverse will be used herein to indicate a movement or axis parallel to the plane of the section 5-5 or 44 of FIGURE 3. Similarly, a reference to longitudinal will be meant to indicate a movement or axial alignment parallel to the plane of section 66 of FIGURE 3.

FIGURE 3 more clearly illustrates the configuration of the four basic jaw inserts 31 to 34. Each of the inserts are seen to be split into mating components, designated by a suflix a or b. Jaw inserts 31 and 32 are fashioned having beveled surfaces 38 and 39 respectively on their outward components 31a and 32a. The bevel is provided in each to cooperate in force transfer relationship with g the tapered interior sidewalls of housing 10. Similarly, a bevel 40 is provided in the outward side of both mating components of jaw insert 33. It will be understood that the configuration and number of such bevels will depend upon the particular internal housing taper involved.

Jaw inserts 31 and 32 are slidably mounted upon the outer surface of base plate 35 in a manner basically allowing only inward and outward movement along an axis transverse to their length. To provide this degree of freedom of movement, component 31a is fastened to a dove insert 42 slidably riding within a complementary keyway 41 machined transversely across base 35 and having an upward surface flush with that of the base member. Attachment to dove 42 is by a socket head machine bolt or screw 43 seated within an appropriate counter bore 44 situate within the dove. (FIGURE 5.) It will be apparent that such a bolted connection provides a sufiicient degree of rigidity for the component 31:: upon the dove inasmuch as additional alignment is imposed by the contiguous internal wall of housing 10.

The inward surface 46 of component 31a lies in plane normal to the surface of base 35 and establishes a force transfer relationship with the parallel surface 47 of mating component 31b. Component 31b is similarly slidably movable along a transverse axis over the surface of base 35; however, it is afforded a greater degree of rotative freedom inasmuch as it is somewhat confined in appropriate alignment between component 31a, the planar surface of a work piece and jaw inserts 33 and 34. This slight rotatability facilitates work piece removal and insertion.

Connection of component 31b to base 35, as shown in FIGURE 5, is by a stripper bolt 49, the head of which rides within a transversely aligned slot-50. Bolt 49, in turn, has a threadless shank portion passing through another transversely aligned slot 51 situate within the movable dove 42, the threadless shank portion then terminating at a lock washer within a recess in component 31b, then being threadably connected to the underside of component 31b. Thusly attached to base 35, the component 31b is capable of sufficient transverse movement independently of mating component 31a to allow for shim insertion and effective closure upon a. work piece or abutting jaw inserts.

To facilitate work piece removal, component 31b is biased outwardly from the center of the gripping structure by a helical spring 53 and plug 54 residing within a transversely-oriented bore 55 in dove 42. The spring will be seen to abut against the end wall 52 of a stationary dove insert 45 situate within keyway 41 and held in place by a pin 36 extending into the base 35.

Looking to the opposite side of the gripping structure, the structure of jaw insert 31 will be seen mirrored in that of jaw insert 32. For instance, outward component 32a is attached to a dove insert 58 by a socket head machine bolt or screw 60, the cylindrical head of which nests within a counter bore 61. Dove insert 58 is slidable within the complementary keyway 41 disposed within base plate 35. Component 32b is slidably connected to base plate 35 by stripper bolt 63, the head of which is slidable within a transversely-oriented slot in base plate 35. Bolt 63, in turn, has a threadless shank portion passing through transversely-oriented slot 66 in dove 58, terminating in an annular lock washer thence being threadably fastened to a tapped bore in component 32b. The outward face 68 of component 32b and the inward face 69 of mating component 32a are parallel surfaces normal to the surface 'of base plate 35 and therefore provide an effective transverse force transfer relationship from the housing wall into the interior of the gripping structure. Component 32b is biased outwardly by a helical spring 71 and plug 72 residing within a transversely-oriented bore 73 in dove 58. The spring abuts against the end wall 74 of stationary dove insert 45 and serves the same purpose as spring 53.

Turning now to the jaw inserts 33 and 34 which are disposed intermediate the above-described inserts 31 and 32, it will be seen that the components of the former are movable along both a longitudinal and transverse axis. Looking initially at the structure of jaw insert 34, it will be observed that both mating components 34a and 34b are slidably mounted upon base 35 by virtue of a dove and keyway attachment. A keyway 77 is machined within component 34a in a manner aligning it with a similar keyway 78 in component 34b. Both keyways ride over a matched dove 80 which is, in turn, aligned transversely upon base 35. Dove 80 is slidably mounted upon base 35 by stripper bolts 81 and 82. The head of bolt 81 (FIGUE 4) rides within a longitudinally-oriented recess 84 in base 35 and, in turn, has a threadless shank portion projecting through longitudinally-oriented slot 85 within the base, the threadless shank terminating at a lock washer upon the base surface, then being threadably connected to the dove 80. The lock washer is selected to fit within a counterbore 86 in the dove. Similarly, stripper bolt 82 has a head riding within a longitudinally-oriented recess 88 at the bottom of base 35 and, in turn, a threadless shank portion projecting through longitudinally-oriented slot 89 within the base, the threadless shank terminating at a lock washer at the surface of the base and then being threadably received within a tapped bore in the underside of dove 80. A counterbore 90 receives the lock washer in dove 80. For convenience, stripper bolts 81 and 82 may be of the socket head variety.

As is portrayed more clearly in FIGURE 6, the dove 80 is provided a longitudinal outward bias by virtue of an arrangement of springs within the base member. In this regard, a helical spring 92 rides within a bore 94 which passes through the longitudinal length of base 35. A plug 93 also rides within the bore 94 and serves to transfer the outward force of the spring to the threadless shank portion of the bolt 82. In similar fashion, a helical spring and plug arrangement situate within longitudinal bore 95 is adapted to urge outwardly the threadless shank of bolt 95. It will be apparent from the foregoing that the abovedescribed springs serve to urge the dove 80 and consequenty the jaw insert components 34a and 34b outwardly along a longitudinal axis for the purpose of facilitating work piece insertion and removal.

By virtue of the dove assembly, mating components 34a and 34b may individually slide along a transverse axis intermediate jaw inserts 31 and 32 and as a result of the stripper boit and slot mounting of dove 80, jaw insert 34 is movable along a longitudinal axis.

The structure and assembly of jaw insert 33 is illustrated in FIGURES 3 and 6. As in the case of jaw insert 34, insert 33 is mounted upon base 35 with a dove and slot arrangement to afford freedom of movement about two axes. Both mating components are machined to provide keyways as at 97 so as to be slidably insertable over -a dove 98. Connection of dove 98 to the base 35 is by two stripper bolts, one of which is shown at 99. The head of stripper bolt 99 rides within a longitudinally aligned recess 101 and, in turn, has a threadless shank portion extending through a correspondingly longitudinally aligned slot 102, the threadless portion terminating at a lock washer, then being threadably connected to a tapped bore in the undersidemf dove 98. A counterbore 103 in dove 98 receives the aforementioned lock washer. For the purpose of facilitating work piece removal, an outward bias is imposed upon dove 98 by the helical spring 92 and plug 105 situate Within longitudinal bore 94. An identical spring and plug assembly situate within parallel longitudinal bore 95 (FIGURES 4 and 5) serves to outwardly bias dove 98 in identical fashion. To simplify the configuration of recess 101, the stripper bolts as shown at 99 may be of the socket head variety.

Returning to FIGURE 3, the interior mutually facing surfaces 48 and 70 of jaw inserts 31 and 32 respectively along with facing surfaces 75 and 76 of jaw inserts 33 and 34 respectively are preferably serrated in order to afford the improved frictional gripping of work pieces held between them. Bevels are also provided along the outward edges of these serrated faces for the purposes of accommodating fillets which may exist between the web and flange of a work piece and for facilitating the imposition of a uniform tensile stress over the gripped work piece.

Operation As is illustrated in connection with FIGURES 1 and 7 through 12, the present gripping structure retains the proven and reliable general configuration of conventional custom fabricated jaw inserts. However, by incorporating split jaw inserts having matched mating components, the structure heretofore described is capable of effectively gripping a myriad of work piece cross-sectional shapes.

The gripping structure is prepared for an individual work piece shapes by selectively positioning within the structure shims 25 formed from a convenient sheet material. A collection of shims, notched to fit over external or exposed doves 80 and 98 and fashioned from a variety of sheet stock thickness has been found desirable where active industrial use is contemplated. As evidenced in the drawings, the shims are inserted where needed between the mated parallel surfaces of the split jaw insert components. When so selectively positioned, the gripping structure is capable of effectively retaining work pieces having varying dimensions in both web and flange. For example, FIGURE 1 depicts shimming for accommodating a Z cross-sectional work piece, and FIGURES 7 and 8 show the gripping structure shimmed to accommodate channels of varying web depth. FIGURES 9 and 10 show the gripping structure shimmed to accommodate I-beams having not only varying web depth, but also varying fiange thicknesses. FIGURE 11 shows a shimming arrangement for an angle member and FIGURE 12 depicts a shimming arrangement for accommodating a T member. From the foregoing discussion and drawings it will be obvious to those skilled in the art that numerous additional shapes in a variety of scales may be conveniently gripped using the structure of the invention and that the gripping structure addition-ally may be readily scaled up or down for use with conventional chuck housings of varying dimension. Further, it may be readily observed that all significant surfaces of the gripped portion of various work pieces are uniformly compressed between two par allel jaw insert surfaces. It is this gripping quality which has heretofore been sought through the use of custom machined jaws. The present structure eliminates the necessity of such custom machining.

When the gripping structure 30 is retracted into the housing 10 following a forming operation, an outward bias at the gripping surfaces expedites work piece removal and jaw preparation for the next forming operation.

While there have been shown and printed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions in the form of detail of the device shown and its method of manufacture may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

Welclaim:

1. A work piece gripping structure for use in conjunction with a stretch press or like machine wherein piston or like means are adapted to urge a jaw-gripping arrangement along the progressively restricting interior surface of a chuck housing, comprising in combination:

(a) a base plate,

(1) having longitudinal and transverse axes, and

(2) adapted to be moved along the interior of said chuck housing;

(b) first and second jaw inserts,

(1) slidably disposed opposite each other in spaced relationship upon said base plate and mutually aligned to be movable along said transverse axis,

(2) each said insert having force transmitting parallel inward faces for gripping a portion of a work piece,

(3) each said insert formed of two separable mating components, and

(4) the respective outward surfaces of said inserts being contoured to transmit an inward force deriving from movement along said housing interior surface;

(c) third and fourth jaw inserts,

(1) intermediate the said inward surfaces of said first and second jaw inserts,

(2) slidably disposed opposite each other in spaced relationship upon said base plate and movable along both said transverse and longitudinal axes,

(3) each said insert respectively having parallel inward faces for gripping a portion of a work piece, and

(4) each said insert formed of two mating components separable along a transverse axis,

(5) the outward surfaces of said inserts being contoured to transmit an inward force from said housing interior surface.

2. The gripping-structure of claim 1 in which the said first and second jaw inserts are biased outwardly from each other, and the said third and fourth jaw inserts are biased outwardly from each other.

3. The gripping structure of claim 1 in which the said mating components of said first and second jaw inserts have parallel mating faces aligned along said longitudinal axis are adapted to transmit said inward [force between said faces.

4. The gripping structure of claim 3 in which:

(a) each of the outermost said mating components of said first and second jaw inserts are connected respectively to a dove member slidably mounted within a matching keyway situated within and aligned transversely across said base plate; and

(b) each of the innermost said mating components of said first and second jaw inserts respectively, are slidably mounted upon said base plate by bolted connection extending into spaced, transversely aligned slots situate within the base plate and said dove members.

5. The gripping structure of claim 3 in which the said mating components of said third and fourth jaw inserts have parallel mating faces aligned along said longitudinal axes.

6. The gripping structure of claim including:

(a) transversely-oriented spring means situated within said base plate and adapted to urge outwardly said first and second jaw inserts, and

(b) longitudinally-oriented spring means situate within said base plate and adapted to urge outwardly said third and fourth ja-w inserts.

7. The gripping structure of claim 1 in which the said mating componets of said third and fourth jaw inserts have parallel mating faces aligned along said longitudinal axes.

8. The gripping structure of claim 7 in which each said mating component of said third and fourth jaw insert respectively is slidably mounted upon a clove member aligned transversely upon the surface of said base plate and slidably movable thereupon in a longitudinal direction.

9. The gripping structure of claim 8 in which each said dove member is slidably mounted upon said base plate by bolted connections extending into longitudinallyaligned slots situate within the base plate.

10. A work piece gripping structure for use in conjunction with a stretch press or like machine wherein piston or like means are adapted to urge a jaw-gripping ((1) each insert of said first pair being split along a line perpendicular to the cross bar of said H-shaped cleavage.

References Cited UNITED STATES PATENTS 2,696,987 12/ 1954- Smith et al 279- 2,850,071 9/1958 Kraybill 72297 2,943,862 7/1960 Myers 27'9-4 2,961,028 11/1960 Bath 72297 CHARLES W. LANHAM, Primary Examiner.

E. M. COMBS, Assistant Examiner.

US. Cl. X.R. 

